Embodiments of the present invention relate in general to event processing, and in particular to techniques for tracking large numbers of moving objects in an event processing system.
Traditional database management systems (DBMSs) execute queries in a “one-off” fashion over finite, stored data sets. For example, a traditional DBMS will receive a request to execute a query from a client, execute the query exactly once against one or more stored database tables, and return a result set to the client.
In recent years, event processing systems have been developed that can execute queries over streams of data rather than finite data sets. Since these streams (referred to herein as “event streams”) can comprise a potentially unbounded sequence of input events, an event processing system can execute a query over the streams in a continuous (rather than one-off) manner. This allows the system to continually process new events as they are received. Based on this processing, the event processing system can provide an ongoing stream of results to a client. One example of such an event processing system is the Oracle Complex Event Processing (CEP) Server developed by Oracle Corporation.
Given their unique capabilities, event processing systems are well-suited for enabling applications that require real-time or near real-time processing of streaming data. For instance, event processing systems are particularly well-suited for building “spatial” applications (i.e., applications that require analysis of streams of spatial or geographic location data). Examples of such spatial applications include geographic information systems (GIS), location-enabled business intelligence solutions, geomatics/telematics applications, and the like. Some event processing systems, such as the Oracle CEP Server, provide an extension mechanism for supporting specific spatial features/operations (e.g., spatial data indexing, proximity and overlap determinations, etc.). Information regarding such an extension mechanism can be found in U.S. patent application Ser. No. 12/949,081, filed Nov. 18, 2010, titled “SPATIAL DATA CARTRIDGE FOR EVENT PROCESSING SYSTEMS,” the entire contents of which are incorporated herein by reference for all purposes.
One limitation with existing event processing systems that allow spatial operations is that they generally cannot support the tracking of a very large number (e.g., greater than one million) of moving geometries or objects. For example, consider use cases from the telematics market where an application needs to (1) determine all of the vehicles impacted by certain traffic events, or (2) detect “buddies” close to a moving vehicle position, where there is an m to n relation between the number of vehicles and buddies using other vehicles. If the total number of vehicles in these use cases is in the range of millions, a conventional event processing system generally cannot index and keep track of all of the vehicles in an efficient manner.